1. Field of the Invention
The present invention relates to optical wiring devices for use in mounting thereon integrated high speed circuitry.
2. Discussion of the Background
Large Scale Integrated circuits (LSIs) are currently capable of operating at remarkably increased speeds due to the increased performance of bipolar transistors and field effect transistors, for example.
However, while the speed of internal operations of LSIs have increased, operation speeds at the level of printed circuit boards including mounted LSI chips and/or racks including printed circuit boards remain less than the LSI operation speeds. When operation frequencies of the printed circuit boards and racks are increased, signal transfer losses of electrical leads, noises and electromagnetic interference are also increased. Thus, it is necessary to lower the operation frequency with an increase in length of the leads used therein to prevent degradation of signals transmitted. Accordingly, currently available electrical wiring devices are incapable of improving the operation speeds, even when the operation speeds of the active LSIs elements are increased, due to the problems at the printed circuit boards and/or racks.
Several approaches have been proposed to avoid the above-noted problems. One approach uses an optical wiring device for optically connecting LSIs. With such an optical wiring/connection, frequency dependency characteristics (such as loss) hardly occur in certain frequency regions ranging from direct current (DC) up to several tens of giga-hertz (GHz). Thus, the lead wiring may offer transfer rates of several tens of gigabits per second (Gbps) because of the absence of any electromagnetic interference and/or ground potential variation noises occurring along signal transmission paths.
To achieve this optical wiring device, leads using optical guide paths or waveguides are required. Generally, connection of optical waveguides is performed through flat plate-like optical waveguide substrates or optical fibers, which can result in a decrease in general-purpose properties or flexibilities compared to electrical lead wiring methodology. Due to this, optical wiring devices are used less in general-purpose applicability than in electrical wiring devices, and are generally only used in special-purpose equipment.
Accordingly one object of the present invention is to provide a novel optical wiring device capable of optically connecting LSI chips, while retaining general-purpose features.
To attain the above object, the present invention provides an optical wiring device including a substrate having a first surface and a second surface on an opposite side of the first surface, and having a hole through the substrate between the first and second surfaces, an integrated circuit disposed on the first surface of the substrate, and an electrical wiring provided on the first surface of the substrate and connected to the integrated circuit. Also included is a photoelectric conversion element provided on the first surface of the substrate and configured to convert between electrical signals and optical signals, and an optical terminal disposed in contact with the hole on a side of the second surface of the substrate. The electrical signals are transmitted between the photoelectric conversion element and the integrated circuit, and the optical signals are transmitted to and from the photoelectric conversion element or through the optical terminal.
In addition, the through-hole in the substrate has a slant side surface for use in performing position alignment of the optical terminal.
It is preferable the optical wiring device has structures as described below.
(1) The optical terminal has a curved plane opposing the photoelectric conversion element.
(2) The hole is provided in a tapered form, and the curved plane of the optical terminal contacts a side surface of the substrate surrounding the hole.
(3) The curved plane of the optical terminal is a part of a spherical surface.
(4) The hole is provided in a tapered form, and the spherical surface of the optical terminal is in contact with a side surface of the substrate surrounding the hole.
The present invention also provides an optical wiring device including a first substrate having a first surface and a second surface on an opposite side of the first surface of the substrate, and having a hole provided through the first substrate between the first and the second surfaces, an integrated circuit disposed on the first surface of the first substrate and a photoelectric conversion element provided on the first surface of the first substrate for conversion between electrical signals and optical signals. Also included is an optical terminal disposed in contact with the hole on the side of the second surface of the first substrate and a second substrate having an optical wiring, and being attached to the first substrate with the optical terminal therebetween. The electrical signals are transmitted between the photoelectric conversion element and the integrated circuit, and said optical signals are transmitted between the photoelectric conversion element and the optical wiring through the optical terminal.
It is preferable the optical wiring device has structures as described below.
(1) The optical wiring runs within the second substrate.
(2) The optical terminal has a curved plane opposing the optical wiring, and an optical focusing point due to the optical terminal being positioned at a portion of the optical wiring.
(3) The second substrate has a concave portion, and the optical terminal has a curved plane in contact with the concave portion of the second substrate so as to be optically coupled to the optical wiring.
(4) The concave portion is provided in a tapered form, and the curved plane of the optical terminal is a part of a spherical surface in contact with a side surface of the concave portion.
(5) The optical focusing point due to the optical terminal is positioned at a portion of the optical wiring deeper than a bottom surface of the concave portion.
(6) An electrical wiring is provided on the first surface of the first substrate and is connected to the integrated circuit.
(7) The optical terminal has a curved plane opposing the photoelectric conversion element.
(8) The hole is provided in a tapered form, and the curved plane of the optical terminal contacts with a side surface of the first substrate surrounding the hole.
(9) The optical terminal has a spherical shape.
(10) The optical terminal has a curved plane opposing the photoelectric conversion element.
(11) The hole is provided in a tapered form, and the curved plane of the optical terminal contacts with a side surface of the first substrate surrounding the hole.
(12) The concave portion is provided in a tapered form, and the optical terminal has a spherical shape.
(13) There is provided an optical connector for optically connecting the optical wiring to another optical wiring, in which the optical connector allows optical signals to be transmitted therein upon application of a pressure thereto.
(14) The optical connector includes a matrix portion and holes dispersed in the matrix portion, and the longest diameter of each of the holes extends in a direction perpendicular to a direction in which the optical signals are transmitted.
(15) The optical connector includes a matrix portion and particles dispersed in the matrix portion, and the refractive index of the particles is higher than the refractive index of the matrix portion.
A principal concept of the invention lies in providing within an integrated circuit (LSI) package structure a package substrate mounting thereon one or more LSI and optical semiconductor element(s) with at least one through-hole provided in the package substrate for alignment in optical axes between an optical semiconductor element and optical input/output terminal having its distal end as formed in either a hemispherical shape or spherical tapered shape.
Another important concept of the invention lies in that a concave portion is provided at an optical input/output section of the optical wiring substrate for mechanical fixation of the optical input/output terminal, while achieving positional alignment between the package substrate and the optical wiring substrate to thereby cause the focal point of a lens of the optical input/output terminal to be put at an optical guide path or xe2x80x9cwaveguidexe2x80x9d which lies inside of the optical wiring substrate.
Yet another feature of the invention is that the power supply and low-speed signal terminals of the integrated circuit are electrically connected via electrical connection pins while permitting high-speed signals to be via one or several photoelectric conversion elements and optical terminals and optical waveguides. Providing electrical power to those electronic components within the integrated circuit in this way, while achieving high-speed signals by use of optical signals, makes it possible to prevent degradation of signals at the board level.
In accordance with the present invention, it is possible to achieve a process separation, which is similar to that of standard LSI mounting schemes such as LSI packages and wiring substrate mounting procedures, because the procedure for an optical axis adjustment between photoelectric conversion elements and optical waveguides is split into an adjustment between the photoelectric conversion elements and optical input/output terminals and an adjustment between optical input/output terminals and optical waveguides.
Thus, it is possible to manufacture the LSI package and the wiring substrate independent of each other while facilitating an increase in size of an optical wiring substrate because the optical lead wiring substrate manufacturing procedure avoids the necessity of mounting photoelectric conversion elements. In addition, the LSI package is such that the use of a specific package substrate with optical terminals provided in advance makes it possible for the LSI package substrate to be put into the standard LSI packaging process flow with a minimal number of extra process steps.
Furthermore, at the stage of mounting the optical wiring substrate, it is possible to achieve mechanical joint or engagement of optical terminals with an accuracy of position alignment equivalent to that of electrical terminals, which enables simultaneous mountabilities with the remaining electronic parts or components, because an individual optical axis alignment is no longer required. Additionally, the position of the focal point of an optical terminal is placed inside of the optical wiring substrate, making it possible to resolve the problem of surface contamination of the optical wiring substrate, thus facilitating a handling thereof.
As discussed above, in accordance with the optical wiring package and optical wiring device incorporating the principles of the present invention, the process steps inherently required for optical wiring/interconnection schemes are simplified or minimized while using the currently established standard electronic parts-mounting techniques. Thus, it is possible to attain the intended optical wiring mounting procedure without having to significantly increase mounting costs so the present invention advantageously offers an ability to construct a system capable of performing an operation at high speeds at the level of boards and racks while reducing production costs.
The present invention also provides an optical wiring device including a first substrate, an integrated circuit disposed on the first substrate, and a photoelectric conversion element provided on the first substrate for conversion between electrical signals and optical signals. Also included is an optical terminal opposing the photoelectric conversion element and a second substrate having a first optical wiring, and being attached to the first substrate with the optical terminal therebetween. The first optical wiring includes a first clad layer and a first optical waveguide surrounded by the first clad layer. Also included is a second optical wiring including a second clad layer and a second optical waveguide surrounded by the second clad layer. In addition, a part of the first optical waveguide is not covered by the first clad layer so as to be exposed therefrom, and the second optical wiring is attached to the first optical waveguide in a direction extending along the first optical waveguide at the part of the first optical waveguide to be exposed. Further, the electrical signals are transmitted between said photoelectric conversion element and said integrated circuit, and said optical signals are transmitted between the photoelectric conversion element and the first and second optical wiring through the optical terminal.
It is preferable that the optical wiring device has structures as described below.
(1) An end portion of the second optical wiring is thinner than other portions thereof at the exposed part of the first optical waveguide.
(2) The first optical waveguide has an end portion in tapered form at the exposed part thereof.
(3) The second optical waveguide has an end portion in tapered form at the exposed part of the first optical waveguide.
The optical connector as described above may be employed in the optical wiring device according to the present invention.
Additionally, the invention provides a method of manufacturing an optical wiring device including an optical wiring substrate having a clad layer formed on or over a substrate, an optical waveguide formed in this clad layer, and an optical contact portion as formed through exposure of the optical waveguide resulting from removal of part of the clad layer. The method includes the steps of disposing, when connecting an optical wire to the optical contact portion of the optical wiring substrate, the optical wire including a resin-based optical waveguide body at the optical contact portion in a direction along the optical waveguide, and then performing connection to the optical contact portion while substantially simultaneously pushing a collect from specified part overlying the optical wire to thereby force a distal end of the optical wire to be deformed into a taper-like shape by ultrasonic wave welding or thermal compression bonding techniques.
In addition, the invention provides an apparatus used for manufacturing an optical wiring device. The apparatus includes a container housing for receiving therein a continuous optical wire, a mechanism for controlling outward delivery or feeding of the optical wire, and a collect for use in rigidly securing the optical wire to an optical contact portion of an optical waveguide while applying thereto a pressure and ultrasonic wave. The collet has at its front and rear portions slant surfaces for permitting segmentation of the optical wire, and the apparatus has functions of letting the optical wire be deformed into a taper-like shape through application of ultrasonic wave and/or heat during bonding, and causing, during cutting of the optical wire, the feed control mechanism to give a tensile force to the optical wire in a pressure application state of the collet to thereby cut the optical wire at a specific portion corresponding to the rear part of the collet.
The present invention is aimed at stabilizing optical waveguide characteristics by making use of a buried type optical guide path for the optical wiring waveguide thereof.
Furthermore, the resultant parts mount density may be increased because connection of the optical wire is in a specific direction along a substrate surface of the optical waveguide without providing the optical waveguide with any orthogonal conversion sections.
Further, with the present invention, any intended optical coupling with the optical wire may be made easier, resulting in prevention of optical losses because the clad layer overlying the optical waveguide is partly removed away at the contact portion.
Furthermore, the present invention further facilitates the optical coupling to thereby reduce optical losses, by forming the optical wire connection section of the optical waveguide into a tapered shape or alternatively forming the optical waveguide connection section of the optical wire into a taper-like shape.
According to present invention, the optical wire is manufactured in advance separately for the improvement in uniformity and reproducibility of optical wire characteristics. Additionally, the present invention makes manufacturing processes easier by employing a resin-made optical waveguide body as the optical wire and also by performing rigid adhesion to the optical waveguide while the optical wire distal end is deformed into a taper shape through ultrasonic wave welding and/or thermo-compression bonding processes.
The present invention also further facilitates connection between the optical waveguide and the optical wire, by using the collet with slant surfaces at its front and rear portions to apply ultrasonic wave or heat or both of them to thereby make the optical wire deform into a taper shape, and by cutting of the optical wire, causing the feed control mechanism to give a tensile force to the optical wire in the pressure application state of the collet.
In addition, the present invention provides an optical coupler device including an optical waveguide body and a pressure sensitive optical filter permitting penetration of rays of light upon application of a pressure thereto. The optical waveguide body is disposed while being pushed against the pressure sensitive optical filter to thereby cause the optical waveguide body and the pressure sensitive optical filter to be optically coupled together.
The present invention also provides an optical coupler device including a first optical waveguide body, a second optical waveguide body, and a pressure sensitive optical filter permitting penetration of light rays upon application of a pressure thereto. The first optical waveguide body and the second optical waveguide body are disposed so they are pushed against the pressure sensitive optical filter whereby the first optical waveguide body and the pressure sensitive optical filter plus the second optical waveguide body are optically coupled together.
The present invention also provides an optical coupler device including an optical waveguide body and a pressure sensitive optical filter permitting penetration of light rays upon application of a pressure thereto and which includes an optical semiconductor element as disposed via the optical waveguide body and the pressure sensitive optical filter. The optical waveguide body is disposed so the body is pushed against the pressure sensitive optical filter to thereby permit the optical waveguide body and the pressure sensitive optical filter to be optically coupled together, and that rays of light emitted and irradiated from the optical semiconductor element are optically guided to travel inside of the optical waveguide body.
The present invention also provides an optical coupler device including an optical waveguide body and a pressure sensitive optical filter permitting penetration of light rays upon application of a pressure thereto and which also includes an optical semiconductor element as disposed via the optical waveguide body and the pressure sensitive optical filter. The optical waveguide body is disposed so the body is pushed against the pressure sensitive optical filter to thereby cause the optical waveguide body and the pressure sensitive optical filter to be optically coupled together, and that light irradiated from the optical waveguide body is received by the optical semiconductor element.
Additionally, the present invention provides an optical coupler device with its pressure sensitive optical filter having an opening or void within an elastic body. Application of a pressure causes the void to shrink in dimension to thereby permit light to pass through it.
In addition, the present invention provides an optical coupler device in which the pressure sensitive optical filter has within the elastic body a plurality of ultrafine or xe2x80x9cmicroxe2x80x9d high-refractivity particles higher in refractive index than the elastic body. A pressure application results in shrinkage of a distance between the micro high-refractivity particles, which in turn permits penetration of light therethrough.
The present invention is such that the optical coupler device is internally provided with the pressure sensitive optical filter for permitting penetration of light when pressed, thereby causing the intended optical coupling to be established only when the ferrule or else of an optical connector is pushed while in the other events blocking rays of light, thus essentially preventing unwanted leakage and mixture of optical signals.